1. Field of the Invention
The present invention relates to a solenoid valve having pressure regulating function and comprising first and second connecting passages and a diaphragm valve which is controlled to keep the pressure in the side of one of the passages under a given pressure and a second multifunctional solenoid valve integrated with the first solenoid valve.
2. Prior Art
There has been employed a pressure regulating solenoid valve having a first connecting passage 31 connected to a fuel tank side and a second connecting passage 32 connected to an intake manifold side and a diaphragm valve 33 for permitting both the first and second connecting passages 31, 32 to communicate with each other, wherein the solenoid valve controls the diaphragm valve 33. The diaphragm valve 33 is moved upward, namely, the diaphragm valve 33 is released from the closing of the communication between the first and second connecting passages 31 and 32 so that the first and second connecting passages 31 and 32 are permitted to communicate with each other when a plunger 35 is pulled upward at the time when the power is turned on to energize a solenoid 34.
There is provided a stator 36 above the plunger 35 for restricting the upward movement of the plunger 35 and also provided a stopper 37 formed of molded rubber or nonmagnetic material and attached to the stator 36 for buffering shock of the plunger 35 which is generated when the plunger 35 strikes against the stator 36.
A spring 38 is provided between the stator 36 and the upper end of the plunger 35. The diaphragm valve 33 is also provided with a check valve 39.
When the solenoid 34 is de-energized, the diaphragm valve 33 is closed by the weight of the plunger 35 and resiliency of the spring 38. When the inner pressure of the fuel tank reaches a given positive pressure, the diaphragm valve 33 is pushed upward so that the pressure is let off to keep the inner pressure of the fuel tank under the given pressure. On the other hand, when the inner pressure of the fuel tank reaches a negative pressure, atmosphere is introduced into the fuel tank from the intake manifold side by way of the check valve 39 so as to permit the inner pressure of the fuel tank to equal the atmosphere.
When the solenoid 34 is energized, the diaphragm valve 33 is open against the weight of the plunger 35 and the resiliency of the spring 38 so as to permit the first connecting passage 31 and the second connecting passage 32 to communicate with each other. As a result, evaporated fuel in the fuel tank is supplied to the intake manifold so as to permit the inner pressure of the fuel tank to be lower than that in the case where the solenoid 34 is de-energized. In case of the negative inner pressure in the fuel tank, the atmosphere is introduced into the fuel tank when the intake manifold side is in the positive pressure but the atmosphere can not be introduced into the fuel tank when the intake manifold side is in the positive pressure. Accordingly, an atmosphere introduction valve is provided in the fuel tank as shown in FIG. 6. The atmosphere introduction valve comprises an atmosphere passage 40, a check valve 41 and a closing valve 43 which is closable by a solenoid 42 of the solenoid valve.
However, there are following problems in the prior art solenoid valve.
(a) Since the plunger 35 is directly connected to the diaphragm valve 33, the diaphragm valve 33 is immediately opened when the solenoid 34 is energized. Accordingly, when an atmosphere opening passage of the canister which is open to the atmosphere is clogged or resistance therethrough is large, the negative pressure in the intake manifold is introduced into the second connecting passage 32, then passes through the diaphragm valve 33 and the first connecting passage 31, whereby the fuel tank is negatively pressurized to apply stress in the fuel tank. As a result, there is a likelihood of breakage of the fuel tank.
(b) Since the stopper 37 formed of the rubber or the nonmagnetic material is attached to the stator 36 by way of sticking of the stopper 37 to the stator 36, if the stopper 37 is detached from the stator 36, the plunger 35 is prevented from being slid. As a result, there is a likelihood that the solenoid valve is prevented from working normally.
(c) Since the pressure regulating solenoid valve and the atmosphere introduction valve are separately provided, both valves need individual spaces for attachment thereof.
(d) Since the evaporated fuel generated in the fuel tank is condensed in the first and second connecting passages 31 and 32 and liquefied therein, there is a likelihood that the valve performance is changed or the evaporated fuel leaks outside, which causes a fire.